The mangrove rivulus Kryptolebias marmoratus a small cyprinodont fish native to tropical and subtropical watersfrom Florida to Brazil, is one of two known self-fertilizing, hermaphroditic vertebrates of which K. marmoratus displays androdioecy,a complex system of reproduction in which hermaphrodites and males are present. This study describes the behavioralrepertoires observed during dyadic interactions in the laboratory. Kryptolebias marmoratus exhibited 23 distinctive acts or behaviors.Acts were divided into four categories: aggressive, submissive, neutral, and reproductive. Leading and following behaviorsplayed important roles in the behavioral repertoires of these fish. In hermaphrodite-male dyads, males exclusively initiatedthe reproductive process and actively pursued hermaphrodites. When hermaphrodites were paired, there was no evidence that theybehaved like other simultaneous hermaphrodites that alternate sexual roles (e.g. serranids). Hermaphrodites were extremely aggressivetowards one another, and the aggressor established dominance rapidly. Male-male dyads were divided into two subdivisionsbased on the presence or absence of the caudal ocellus on one fish. A caudal ocellus on one male appeared to signal the possibilityof a potential mating partner to males lacking it. Pairings of males without an ocellus were similar to hermaphrodite-hermaphrodite dyads in that both members of the pair were aggressive towards one another. These observations may be indicativeof interactions taking place in natural communities or assemblages of fish in which both males and hermaphrodites occurand provide evidence on the role of dyadic interactions in the mixed-mating
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